What is the preferred renal replacement therapy, Continuous Renal Replacement Therapy (CRRT) or Sustained Low-Efficiency Dialysis (SLED), for critically ill patients with acute kidney injury and hemodynamic instability?

SLED vs CRRT for Critically Ill Patients with AKI

For hemodynamically unstable critically ill patients with acute kidney injury, use CRRT as the preferred modality, but SLED is an acceptable and reasonable alternative when CRRT is unavailable or resource-constrained. 1

Primary Recommendation Based on Guidelines

CRRT is the guideline-recommended modality for hemodynamically unstable patients with AKI. The KDIGO guidelines, endorsed by KDOQI, suggest using CRRT rather than standard intermittent hemodialysis for hemodynamically unstable patients (Grade 2B recommendation). 1 The Surviving Sepsis Campaign similarly suggests either CRRT or intermittent RRT, with CRRT preferred for facilitating fluid balance management in hemodynamically unstable septic patients. 1

The Case for SLED as an Alternative

SLED represents a "hybrid" modality that can be safely used in hemodynamically unstable adult patients and warrants consideration as a practical alternative. 1 The KDOQI Work Group explicitly states that prolonged intermittent RRT modalities (PIRRT/SLED) are reasonable alternatives to CRRT in hemodynamically unstable adult patients, though they note additional clinical research is needed to compare outcomes and cost-effectiveness. 1

Advantages of SLED:

• Combines benefits of both modalities: Uses classic dialysis hardware at low blood and dialysate flow rates for prolonged periods (6-12 hours/day), offering more hemodynamic stability than standard intermittent hemodialysis while avoiding the resource demands of CRRT. 2
• Better hemodynamic tolerance than standard HD: Provides more adequate solute removal and better correction of hypervolemia compared with intermittent hemodialysis. 2
• Resource efficiency: Reduces nursing and equipment demands compared to 24-hour CRRT while maintaining clinical effectiveness. 3

Clinical Outcomes: SLED vs CRRT

The most recent comparative evidence shows no significant difference in mortality or clinical outcomes between SLED and CRRT. A 2015 cohort study of 232 critically ill patients found 30-day mortality of 54% with SLED versus 61% with CRRT (adjusted OR 1.07,95% CI 0.56-2.03). 3 Risk of RRT dependence at 30 days (adjusted OR 1.36,95% CI 0.51-3.57) and early clinical deterioration (adjusted OR 0.73,95% CI 0.40-1.34) were not different between modalities. 3

Importantly, the Surviving Sepsis Campaign found no mortality difference between continuous and intermittent RRT in septic patients. Five prospective RCTs showed no significant survival difference, with the largest trial of 360 patients confirming this finding. 1

When to Choose CRRT Over SLED

CRRT remains the preferred choice in specific high-risk scenarios:

• Acute brain injury with increased intracranial pressure or cerebral edema: CRRT provides slower solute flux per unit time, resulting in slower solute shifts that are better tolerated by patients with intracranial pathology. 1, 4
• Severe hemodynamic instability requiring continuous fine-tuning: CRRT allows for continuous adjustment of intravascular volume and better management of severe fluid overload. 1, 5
• Patients requiring continuous removal of inflammatory mediators: Such as those with septic shock, ARDS, or severe burns. 5

Practical Implementation Considerations

For CRRT (when chosen):

• Deliver effluent volume of 20-25 mL/kg/hour as the standard dose. 1, 4, 5
• Use regional citrate anticoagulation as first-line in patients without contraindications. 1, 4, 5
• Monitor delivered versus prescribed dose frequently and adjust iteratively. 4, 6

For SLED (when chosen):

• Target 8 hours per session with blood flow of 200 mL/min. 3
• Can be performed without anticoagulation in patients with bleeding risk, reducing hemorrhagic complications. 3
• Use low dialysate flow rates to maintain hemodynamic stability while achieving adequate solute clearance. 2

Common Pitfalls to Avoid

• Don't dismiss SLED based solely on older guidelines: The evidence base shows equivalent outcomes, and SLED addresses practical resource limitations in many ICUs. 3
• Don't use standard intermittent hemodialysis in hemodynamically unstable patients: This is associated with worse hemodynamic tolerance and should be avoided. 1, 2
• Don't fail to monitor actual delivered dose: Prescribed dose often differs significantly from delivered dose, impacting clinical outcomes. 4, 6
• Avoid subclavian vein access: Use right internal jugular as first choice, then femoral, then left internal jugular, with subclavian as last resort. 1, 4, 5

Bottom Line Algorithm

Use this decision pathway:

1. Patient has acute brain injury/increased ICP/cerebral edema? → Choose CRRT 1, 4
2. Patient has severe, refractory hemodynamic instability requiring continuous adjustment? → Choose CRRT 1, 5
3. Patient is hemodynamically unstable but stabilizable, and CRRT resources are limited? → SLED is acceptable 1, 3
4. Patient is hemodynamically stable? → Standard intermittent hemodialysis is appropriate 1

The key distinction is that while CRRT remains the guideline-preferred modality for hemodynamic instability, SLED represents a clinically equivalent alternative when CRRT is not feasible or available. 1, 3